The quantity needed is calculated 2 different ways

When the purchased package is 1. (Sheets, Machining Stock)
You will divide 1 by how many pieces you get from the piece.
If I can get 19 pcs per sheet, quantity needed will be calculated
by dividing 1/19=0.0526

When the purchsed package is greater than 1. (Box of screws, bolts)
You will divide how many pieces the unit requires from the customers print
by how many pieces come in the purchased package
If I need 15 screws per units and the package of screws is 100 per box
quantity needed will be calculated by dividing 15/100=0.15

You can type the formula in this field such as 15/100

If you leave this field blank it will assume 1.